WPF Triggers in VB.NET
This tutorial shows how to implement different types of triggers in WPF Application.
Trigger is a feature that allows a user to dynamically change the appearance and behavior of a control in an application without having to create a new control in WPF. It sets properties of controls or starts its actions when a property value changes or when an event is raised.
Mouseover effects are a very common application of triggers. Triggers can fully be expressed using XAML, eliminating the need to write code for many simple effects.
There are three types of triggers in WPF:
Property Triggers - It run when the value of a dependency property changes. Property triggers are used to monitor a DependencyProperty's value. Here we applies a glow effect to a button when the mouse pointer is over the button (IsMouseOver=true).
Property Trigger Code
<Window x:Class="WpfApplication1.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<Canvas>
<Canvas.Resources>
<Style TargetType="{x:Type Button}">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="BitmapEffect">
<Setter.Value>
<OuterGlowBitmapEffect GlowColor="Gold" GlowSize="10" />
</Setter.Value>
</Setter>
</Trigger>
</Style.Triggers>
</Style>
</Canvas.Resources>
<Button Canvas.Left="29" Canvas.Top="29" Width="75" Height="42">Click Me</Button>
</Canvas>
</Window>
Output
After Mouse Over
Data Triggers - DataTrigger represents a trigger that applies property values or performs actions when the bound data meets a specified condition. It run when the value of any .NET property changes, using data binding.
Data Trigger Code
<StackPanel>
<StackPanel Orientation="Horizontal">
<StackPanel.Style>
<Style TargetType="{x:Type StackPanel}">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=IsChecked, ElementName=RadioButton3}" Value="True">
<Setter Property="IsEnabled" Value="False"/>
</DataTrigger>
<DataTrigger Binding="{Binding Path=IsChecked, ElementName=RadioButton4}" Value="True">
<Setter Property="IsEnabled" Value="False"/>
</DataTrigger>
</Style.Triggers>
</Style
</StackPanel.Style>
<RadioButton Name="RadioButton1"/>
<RadioButton Name="RadioButton2"/>
<RadioButton Name="RadioButton3"/>
<RadioButton Name="RadioButton4"/>
</StackPanel>
<Button Content="Data Trigger" Click="Button_Click"/>
<x:Code>
<![CDATA[
private void Button_Click(object sender, RoutedEventArgse)
{
RadioButton2.IsChecked = true;
}
]]>
</x:Code>
</StackPanel>
Output
Event Triggers - Event triggers watch for events. When an event happens, such as a Click event, an event trigger responds by raising an animation related action.
Event Trigger Code
<StackPanel>
<ToggleButton Name = "button">
<ToggleButton.Template>
<ControlTemplate TargetType="ToggleButton">
<TextBlock> Click Me Here!!</TextBlock>
</ControlTemplate>
</ToggleButton.Template>
</ToggleButton>
<Popup IsOpen="{Binding IsChecked, ElementName=button}">
<Border Background="LightYellow">
<TextBlock> I'M the popup</TextBlock>
</Border>
</Popup>
</StackPanel>
Output
Conclusion
Here we discussed about different types of Trigger implementations in WPF.